Stochastic modelling of ion diffusion in complex systems

Fast ion conduction is known to occur in many solid materials, allowing us to perform fundamental studies of diffusion processes in a variety of structures. After briefly discussing classes of solid ionic conductors with increasing complexity in their structural and transport behaviour, we shall focus on polymer electrolytes. A lattice model is described which emphasizes the asymmetry in the cation-polymer and anion-polymer interactions. Monte-Carlo simulations of the equation of state are supplemented by calculations based on the quasi-chemical approximation. Simulated diffusion constants and their dependence on temperature and ion concentration are compared with recent experiments on PEO (polyethylene oxid)-type conductors